Method and apparatus for providing communication using a terahertz link

ABSTRACT

A method and apparatus for establishing a terahertz link using a multi-element lens array that comprises a liquid lens are disclosed. For example, the method receives detected terahertz signals from one or more detectors, where a liquid lens is deployed with each of the one or more detectors. The method determines, for each of the detected signals, if the detected signal is out of focus, and applies a corrective voltage to each liquid lens that corresponds to a detected terahertz signal that is out of focus, wherein the corrective voltage adjusts a focus of the detected signal. The method measures a signal-to-noise ratio of the detected signals, and establishing a terahertz link via at least one of the detected terahertz signals with a highest signal-to-noise ratio.

The present disclosure relates generally to communication using aterahertz link and, more particularly, to a method for providingcommunication over a terahertz link using a multi-element lens arraythat comprises a liquid lens.

BACKGROUND OF THE DISCLOSURE

The increasing utilization of mobile personal devices, e.g., cellphones, smart phones, etc., has dramatically increased network traffic.For example, fully one billion people worldwide are Internet users witha large portion of this population accessing the Web through theirmobile phones. In addition, the behavior of mobile phone customers haschanged in recent years. The number of users accessing media-rich dataand social networking sites via mobile personal devices has risendramatically. For example, the average owner of a smart phone todaytransacts three times the amount of data than did early smart phoneusers. Consequently, there is a need to continually grow the networkcapacity to accommodate the ever increasing traffic.

But as is often the case, with great success also comes greatchallenges. For example, some cellular service providers are strugglingto keep up with demand and they are placing limits on data usage toconserve network bandwidth and spectrum. This industry pushback isclearly a reaction to the recognition of the bandwidth and capacitylimits of existing cellular systems. However, placing limits on datausage is an unpractical approach to reduce demand, which also reducesrevenue for the service provider and creates dissatisfaction forcustomers.

SUMMARY OF THE DISCLOSURE

In one embodiment, the present disclosure teaches a method and apparatusestablishing a terahertz link using a multi-element lens array thatcomprises a liquid lens. For example, the method receives detectedterahertz signals from one or more detectors, where a liquid lens isdeployed with each of the one or more detectors. The method determines,for each of the detected signals, if the detected signal is out offocus, and applies a corrective voltage to each liquid lens thatcorresponds to a detected terahertz signal that is out of focus, whereinthe corrective voltage adjusts a focus of the detected signal. Themethod measures a signal-to-noise ratio of the detected signals, andestablishing a terahertz link via at least one of the detected terahertzsignals with a highest signal-to-noise ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

The teaching of the present disclosure can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates a sectional view of a transmitter with a fly's eyestructure;

FIG. 2 illustrates an exemplary communications link established betweenthe transmitter and a receiver;

FIG. 3 illustrates a block diagram depicting an exemplary networkrelated to the current disclosure;

FIG. 4 illustrates a flowchart of a method for providing communicationusing a THz link; and

FIG. 5 illustrates a high-level block diagram of a mobile devicesuitable for use in performing the functions described herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

The present disclosure broadly teaches a method and apparatus forproviding communication over a terahertz link using a mobilecommunication device having a multi-element lens array that comprises aliquid lens, that is capable of communicating with a network, e.g., viaa base station. In turn, the communication can be extended into thenetwork, thereby allowing the mobile device to access various servicesover the network. Although the present disclosure is discussed below inthe context of wireless networks, e.g., cellular networks, the presentdisclosure is not so limited. Namely, the present disclosure can beapplied to all networks that would benefit from improved control of adirectionality of terahertz signals transmitted to and from mobiledevices, e.g., laptops, mobile phones, and the like.

In one embodiment, the current method enables expansion of networkcapacity by employing wireless Local Area Networks (LANs) that operatein a terahertz (THz) spectrum. Devices that operate in the THz spectrumby definition use a Terahertz frequency. A critical consideration forusing THz frequencies is related to the sizes of the terahertz antennas.The wavelength of a waveform whose frequency is in the order of a THz isvery small. As the wavelength becomes smaller, the antenna's aperture,(i.e., the area over which the antenna collects or launches anelectromagnetic wave), is correspondingly reduced. Conventionalmicrowave cellular radios have antennas that are on the order of inchesin length. But as wavelengths get smaller, and especially in the higherfrequency domains of THz frequencies, antennas can shrink to literallymicroscopic proportions. The proportion of radio energy intercepted andcollected by so small an antenna is quite small, dramatically reducingthe reach of signals transmitted over terahertz frequency.

One approach for improving the reach of transmitted signals is to placea lens, e.g., a dielectric lens, in front of the transmitting andreceiving antennas. The combination of the antenna and lens has animproved gain. Unfortunately, the improvement in the gain comes at acost in terms of directionality. Specifically, a signal (also referredto as a beam) transmitted by a combination of an antenna and a lens(placed in front of the antenna) is highly directional and may bereferred to as an omni-directional signal. Furthermore, the gain of thelens increases as the solid angle (measured in steradians) illuminatedby the antenna decreases. In order to achieve a high gain, the solidangle illuminated by the antenna has to become quite small. The highlydirectional nature of the transmitted signal and the need to minimizethe solid angle illuminated by the antenna, to achieve the desired gain,create a challenge for beam alignment between the transmitter andreceiver antennas. For example, if a mobile device, e.g., a mobilephone, is attempting to communicate with a base station over a THzfrequency, the transceivers in the mobile phone and the base station maynot succeed in establishing a communications link.

In one embodiment, the current method teaches a beam alignment (signalalignment) between the transmitter and receiver antennas using aspherical structure and a hemispherical structure for the transmittingand receiving antennas, respectively. The transmitter and receiver maybe combined to share circuitry and housing. In such embodiment, thecombination of the transmitter and receiver is referred to as atransceiver. A transceiver that has a spherical structure fortransmitting and a hemispherical structure for receiving is alsoreferred to as a fly's eye structure.

The spherical structure is used for transmitting a plurality of signals,with each signal aimed outward from the center of the sphere, such thatthe plurality of the signals covers an entire three dimensional space.Similarly, the hemispherical structure is used for receiving a pluralityof signals, with each signal being received by a combination of anantenna and a lens. The hemispherical structure for receiving aplurality of signals may be a cluster of receivers, wherein eachreceiver has a combination of an antenna and a lens. In one embodiment,the combined field of view of all of the receivers in a cluster covers ahemisphere or a near hemisphere.

In one embodiment, the current method teaches using individualintegrated transceivers directly behind a combination of an antenna anda lens. The individual integrated transceivers are connected to thecombination of the antenna and lens, wherein the lens is made of adielectric material.

FIG. 1 illustrates a sectional view of a transmitter 100 with a fly'seye structure. In one embodiment, the transmitter 100 comprises an array105 of a plurality of combinations 106 a-106 i, wherein each of thecombinations 106 a-106 i comprises a corresponding THz source 108 a-108i connected to an antenna 111 a-111 i, and a lens 115 a-115 i. Forexample, the combination 106 a comprises a THz source 108 a connected toan antenna 111 a, and a lens 115 a. Similarly, the combination 106 bcomprises a THz source 108 b connected to an antenna 111 b, and a lens115 b, and so on. Each of a plurality of signals 117 a-117 i is aimedoutward from a center of the sphere 119.

The combination of: (1) transmitting using many directed signals; and(2) receiving using a cluster of receivers, increases the likelihood ofestablishing a link between a transceiver in a mobile device and anothertransceiver, e.g., in a base station. Specifically, a signal from amongall the signals received by the cluster of receivers may be selected.For the example above, a transceiver in a device may detect one of moreof the plurality of signals 117 a-117 i transmitted by another device.One of the plurality of signals 117 a-117 i may then be selected by thereceiving device.

In one embodiment, the service provider may configure a plurality ofcriteria for selecting a particular signal. For example, the selectionmay be based on avoidance of link shadowing, Signal-To-Noise Ratio(SNR), etc. SNR refers to a measure of signal strength relative tobackground noise usually measured in decibels (dB). For example, the SNRfor each of the signals received by the cluster of receivers can bemeasured and the signal with the highest SNR will be selected.

However, the user of the mobile device may change his/her location andmay lose a connection. Hence, maximizing the reach of the system mayneed active steering of the highly directional signals based on apositional relationship between a transceiver in the mobile device and atransceiver in the base station. Furthermore, as described above,receivers operating in THz frequencies have very small aperture (e.g.,in the order of microns in diameter). Therefore, each lens implementedin the cluster of receivers may need to accurately focus the collectedTHz energy onto a small detector.

However, as described above, THz frequencies travel very shortdistances. The near-field nature of the THz transmitters and receivershas the following challenges:

-   -   A slight movement of the transceivers will change the focal        point of the received signal (beam);    -   The receiving lens may steer a focusing signal (beam) to a focus        spot which is offset from the small detector area of the        receiver, possibly failing to illuminate the detector entirely;        and    -   If the focus spot moves away from the ideal optical axis (i.e.,        the transmitted signal and lens axis are not perfectly aligned),        the resulting focus spot may be many times larger and of lower        average energy, than the ideally designed focal spot, rendering        a lower link margin.

In one embodiment, the current method teaches an active and adaptivecontrol of the focus point (spot) using a liquid lens to optimize THzsignal detection. In one embodiment, a liquid lens is a lens made fromtwo liquids of varying density sandwiched between two windows in aconical vessel. For example, the liquids may be two types of oils havingdifferent density, e.g., olive oil, vegetable oil, rape seed oil, grapeseed oil, polyglycol oil and the like. It should be noted that otherliquids in addition to oil can be used. The type of liquids may beselected based upon on a desired behavior such as the ability to allowpassage of THz signals without degrading or distorting the THz signals.For example, various illustrative liquids that can used are disclosed inGorenflo et al., “Dielectric properties of-oil-water complexes usingterahertz transmission spectroscopy”, Chemical Physics Letters, 421,494-498 (2006).

Specifically, if a voltage is applied across the conical structure, theshape of the interface between the two types of liquid changes. Forexample, if zero volts are applied, the shape of the interface will beflat, whereas if 40 volts are applied, the shape will be highly convex.The ability to manipulate the shape of the interface between the twoliquids allows for electronic control of certain properties of the lens.Hence the selection of the liquids may be based on a desired shape ofthe interface between the two liquids. For example, a far field imaginglens (e.g., a regular lens) can be changed to a near field imaging lenscapable of taking microscopic type images. The liquid lens is small insize and can be fitted into an array of lenses.

In one embodiment, the current method provides an active control topre-distort the shape of the liquid lens to compensate for a shift inimage. That is, the method pre-distorts a signal to compensate for adistortion that would exist from a signal received with an offset fromthe optical axis 228 shown in FIG. 2 below. Thus, as the angle of thereceived signal changes, the shape of the liquid lens is activelyadjusted to dynamically control the focal point.

In one embodiment, the liquid lens is positioned between each of thedetectors and a primary lens of the fly's eye structure. For example,each of a plurality of liquid lenses may be designed to opticallyoperate in conjunction with a fixed primary lens, e.g., a silicon lens.The liquid lens adjusts the focusing power of the corresponding primarylens. In one embodiment, a software or electronic system adjusts theshape of the liquid lens, thereby adjusting the focusing power of thecombination of the liquid lens and the fixed primary lens.

FIG. 2 illustrates an exemplary communications link 200 establishedbetween the transmitter 100 and a receiver 220. The receiver 220comprises an array of a plurality of combinations, wherein each of thecombinations comprises a liquid lens 230 a-n positioned between each ofits detectors 221 a-n and a primary lens 225 a-n. For example, acombination comprises a liquid lens 230 a positioned between a detector221 a and a primary lens 225 a. Similarly, each of the othercombinations (not shown) has a liquid lens positioned between a detectorand a primary lens. It should be noted that although only onecombination is shown in the receiver 220 for clarity reasons, there arein fact a plurality of such combinations that can be configured into ahemispherical configuration or a hemispherical configuration. Thecombination of the primary lens 225 a and liquid lens 230 a with theassistance of a variable voltage source 229 focuses the signals 117 eonto the focus point 222 onto a THz detector 221. For example, if thefocus point of signal 117 e is off-set, then the shape of the interfaceof the liquid lens 230 is dynamically adjusted via processor 231 toensure the signal is focused back at the focus point 222.

Note that any number of the plurality of signals 117 a-117 i may bereceived. For example, another detector (not shown) may receive thesignal 117 d. The combination of: (1) transmitting using many directedsignals; and (2) receiving using a cluster of receivers, increases thelikelihood of establishing a link between a transceiver in a mobiledevice and a transceiver in a base station. Specifically, a signal fromamong all signals received by the cluster of receivers can be selected.For the example above, a transceiver in a device may detect one or moreof the plurality of signals 117 a-117 i transmitted by another device.One of the signals 117 a-117 i may then be selected by the receivingdevice based on the SNR or any other established criteria.

FIG. 3 illustrates a block diagram depicting an exemplary network 300related to the current disclosure. The network 300 comprises a pluralityof mobile devices 301-303 configured for communicating with a corenetwork 310 via a wireless Local Area Network (LAN) 305. The LAN 305comprises base stations 311-313. The base stations provide mobiledevices with connectivity for forwarding received signals to the network310. Each of the mobile devices 301-303 may communicate with one or moreof the base station 311-313 via a THz frequency.

In one embodiment, the service provider may implement the current methodin the mobile devices 301-303 and base stations 311-313. That is, theservice provider may implement transceivers with a fly's eye structurein the mobile devices and base stations. A liquid lens is positionedbetween each pair of detectors and primary lenses in the fly's eyestructure. A controller in the mobile device or base station thendetermines if a received signal is out of focus. For example, signalsreceived from two of ten detectors may be out of focus. The two signalsthat are out of focus may then need corrective action. The controllermay then apply a corrective voltage to the liquid lens that correspondsto the detector whose signal is out of focus. Specifically, thecontroller adjusts the shape of the interface of the liquid lens,thereby adjusting the focusing power of the combination of the liquidlens and the fixed primary lens. For example, the liquid lensesassociated with the two detectors that received an out of focus signalare identified. The method then applies an appropriate voltage such thata focused signal is received by their respective detectors.

Those skilled in the art will realize that although only three mobiledevices, three base station and one LAN are depicted in FIG. 3, thecommunication system 300 can be expanded by including any number ofmobile devices, access networks, network elements, without altering thescope of the present disclosure.

In one alternate embodiment, the two optical stage arrangement (fixedlens and liquid lens) as discussed above can modified by replacing thefixed lens with a second adaptive liquid lens that would function as theprimary lens. The use of two liquid lenses rather than one may allow fora greater adaptive focus control response and less severe liquid lenscurvatures in either lens stage. This alternate embodiment will alsorequire less electrical power and thus will prolong battery life in themobile devices.

FIG. 4 illustrates a flowchart of a method 400 for providingcommunication using a THz link. In one embodiment, one or more steps ofmethod 400 can be implemented in a mobile device or a base station. Forexample, the method 400 may be performed by a controller in a mobiledevice or a base station. Method 400 starts in step 405 and proceeds tostep 410.

In step 410, method 400 receives detected THz signals from one or moredetectors employing a liquid lens. For example, a liquid lens may beemployed by each of a plurality of detectors in a transceiver with afly's eye structure. The liquid lens (broadly a first lens) ispositioned between its corresponding fixed lens (broadly a second lens)and a THz signal detector. The controller may then receive detected THzsignals from each of the one or more detectors in the fly's eyestructure.

In step 420, method 400 determines, for each of the detected THzsignals, if the detected THz signal is out of focus. For example, one ormore of the THz signals may be received with an offset from the opticalaxis.

In step 425, method 400 determines if all the detected signals are infocus. If all the detected THz signals are in focus (no detected signalis out of focus), the method proceeds to step 440. Otherwise, the methodproceeds to step 430.

In step 430, method 400 applies a corrective voltage to each of aplurality of liquid lenses that correspond to a THz signal that is outof focus, wherein the corrective voltage adjusts the focus of thedetected THz signal such that the detected signal is received in focus,or to a greater degree of focus if the offset is too great to be fullycorrected. Specifically, the controller adjusts the shape of theinterface of the liquid lens associated with the detector that receivedthe out of focus signal by applying an appropriate voltage such that afocused signal is received by the corresponding detector.

In step 440, method 400 measures the Signal-to-Noise Ratio (SNR) ofdetected signals. For example, the method may have received severalsignals in focus but they may have different SNRs. In another example,some signals may have been received via a corrective action (via theliquid lens) while other signals were in focus without any correctiveaction. SNRs are then measured for all the received signals (with orwithout the liquid lens) from all the detectors.

In step 450, method 400 establishes a THz link via the detected signalwith a highest SNR. For example, the method selects the detected signalwith a highest SNR and the THz link between two devices (e.g., a mobiledevice and a base station) is established over the selected signal. Itis important to note that the selected signal may be a signal receivedvia a corrective action or without the corrective action. It should benoted that there may be a feedback path between steps 430 and 440, wherethe measured SNR can be used to fine tune the amount of voltage to applyto each of the liquid lens.

The method then proceeds to step 460 to end processing the detectedsignals or alternatively to step 410 to continue receiving more detectedsignals.

It should be noted that although not specifically specified, one or moresteps of method 400 may include a storing, displaying and/or outputtingstep as required for a particular application. In other words, any data,records, fields, and/or intermediate results discussed in the method canbe stored, displayed and/or outputted to another device as required fora particular application. Furthermore, steps or blocks in FIG. 4 thatrecite a determining operation or involve a decision, do not necessarilyrequire that both branches of the determining operation be practiced. Inother words, one of the branches of the determining operation can bedeemed as an optional step.

It should be noted that the mobile device may comprise various userinterfaces for facilitating communication. For example, a user interfacemay include a physical button or key on the mobile device for selectingfrequency spectrum, e.g. THz versus cellular.

FIG. 5 depicts a high-level block diagram of a general-purpose computersuitable for use in performing the functions described herein. Asdepicted in FIG. 5, the system 500 comprises a processor element 502(e.g., a CPU or a controller), a memory 504, e.g., random access memory(RAM) and/or read only memory (ROM), a module 505 for providingcommunication using a THz link, and various input/output devices 506(e.g., storage devices, including but not limited to, a tape drive, afloppy drive, a hard disk drive or a compact disk drive, a receiver asdiscussed above, a transmitter as discussed above, a transceiver asdiscussed above, a speaker, a display, a speech synthesizer, an outputport, and a user input device (such as a keyboard, a keypad, a mouse,alarm interfaces, power relays and the like)).

It should be noted that the present disclosure can be implemented in acombination of software and hardware, e.g., using application specificintegrated circuits (ASIC), a general-purpose computer or any otherhardware equivalents. In one embodiment, the present module or process505 for providing communication using a THz link can be loaded intomemory 504 and executed by processor 502 to implement the functions asdiscussed above. As such, the present method 505 for providingcommunication using a THz link (including associated data structures) ofthe present disclosure can be stored on a non-transitory computerreadable storage medium, e.g., RAM memory, magnetic or optical drive ordiskette and the like.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A method for establishing a terahertz link,comprising: receiving, by a processor, detected terahertz signals from aplurality of detectors, where a liquid lens is deployed with each of theplurality of detectors; determining, by the processor, for each of thedetected signals, if the detected signal is out of focus; applying, bythe processor, a corrective voltage to each liquid lens that correspondsto a detected terahertz signal that is out of focus, wherein thecorrective voltage adjusts a focus of the detected signal; measuring, bythe processor, a signal-to-noise ratio of the detected signals; andestablishing, by the processor, a terahertz link via one of the detectedterahertz signals with a highest signal-to-noise ratio.
 2. The method ofclaim 1, wherein the receiving the detected terahertz signals isperformed by a cluster of the plurality of detectors having a combinedfield of view that is hemispherical.
 3. The method of claim 1, whereineach liquid lens is deployed between a respective detector of theplurality of detectors and a primary lens.
 4. The method of claim 3,wherein the primary lens comprises a second liquid lens.
 5. The methodof claim 1, wherein the applying of the corrective voltage is performedby the processor that adjusts a shape of an interface of the liquidlens.
 6. The method of claim 1, wherein the detected signals aretransmitted by a transmitter, with each of the detected signal beingaimed outward from a center of a spherical structure.
 7. The method ofclaim 1, wherein the detected terahertz signals are received by a mobiledevice.
 8. The method of claim 1, wherein the detected terahertz signalsare received by a base station.
 9. A tangible computer-readable storagemedium storing a plurality of instructions which, when executed by aprocessor, cause the processor to perform operations for establishing aterahertz link, the operations comprising: receiving detected terahertzsignals from a plurality of detectors, where a liquid lens is deployedwith each of the plurality of detectors; determining, for each of thedetected signals, if the detected signal is out of focus; applying acorrective voltage to each liquid lens that corresponds to a detectedterahertz signal that is out of focus, wherein the corrective voltageadjusts a focus of the detected signal; measuring a signal-to-noiseratio of the detected signals; and establishing a terahertz link via atI act one of the detected terahertz signals with a highestsignal-to-noise ratio.
 10. The tangible computer-readable storage mediumof claim 9, wherein the receiving the detected terahertz signals isperformed by a cluster of the plurality of detectors having a combinedfield of view that is hemispherical.
 11. The tangible computer-readablestorage medium of claim 9, wherein each liquid lens is deployed betweena respective detector of the plurality of detectors and a primary lens.12. The non transitory tangible computer-readable storage medium ofclaim 11, wherein the primary lens comprises a second liquid lens. 13.The tangible computer-readable storage medium of claim 9, wherein theapplying of the corrective voltage is performed by the processor thatadjusts a shape of an interface of the liquid lens.
 14. The tangiblecomputer-readable storage medium of claim 9, wherein the detectedsignals are transmitted by a transmitter, with each of the detectedsignal being aimed outward from a center of a spherical structure. 15.The tangible computer-readable storage medium of claim 9, wherein thedetected terahertz signals are received by a mobile device.
 16. Thetangible computer-readable storage medium of claim 9, wherein thedetected terahertz signals are received by a base station.
 17. Areceiver, comprising: a plurality of first lens; a plurality of liquidlens; a plurality of detectors, for receiving a plurality of terahertzsignals, wherein one of the plurality of first lens is arranged with acorresponding one of the plurality of liquid lens and with acorresponding one of plurality of detectors to form a respectivecombination, wherein when one of the plurality of terahertz signals isreceived by a respective combination and is out of focus, then avariable voltage source applies a voltage to a respective liquid lens tofocus one of the plurality of terahertz signals onto a respectivedetector; and a processor for measuring a signal-to-noise ratio of eachof the plurality of terahertz signals to determine whether one of theplurality of terahertz signals is received out of focus.
 18. Thereceiver of claim 17, wherein the plurality of first lens comprises asecond set of liquid lens.
 19. The receiver of claim 17, wherein thereceiver is deployed in a mobile device.